dt-bindings: rcar-{csi2,vin}: Rename bindings documentation files

Renesas media binding documentation files use a naming schema of
'renesas,<module>.txt'. Rename the VIN and CSI-2 files to match this
pattern.
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

MAINTAINERS

@@ -10017,8 +10017,8 @@ L:	linux-media@vger.kernel.org
 L:	linux-renesas-soc@vger.kernel.org
 T:	git git://linuxtv.org/media_tree.git
 S:	Supported
-F:	Documentation/devicetree/bindings/media/renesas,rcar-csi2.txt
-F:	Documentation/devicetree/bindings/media/rcar_vin.txt
+F:	Documentation/devicetree/bindings/media/renesas,csi2.txt
+F:	Documentation/devicetree/bindings/media/renesas,vin.txt
 F:	drivers/media/platform/rcar-vin/
 
 MEDIA DRIVERS FOR RENESAS - VSP1